This disclosure relates generally to a blade and a disk within a turbomachine. More particularly, this disclosure relates to redistributing loads on the disk and a base of the blade by adjusting the interface between the disk and the base of the blade.
Turbomachines are well known. Turbomachines typically include multiple rotor assemblies within a fan assembly, a compressor section, and a turbine section. The rotor assemblies each include an array of blades circumferentially distributed about a rotational axis of the turbomachine. The blades each include a base section, a platform section, and an airfoil section that extends radially outwardly from the platform section.
During assembly, the base section is received within a recess established within an outer rim of the disk. The base has multiple lobes that contact areas of the disk to limit radial movement of the blade relative to the disk. Such a base is sometimes referred to as a fir-tree base. As the turbomachine reaches an operating speed, centrifugal forces cause the base to move within the recess from an unloaded position and a loaded position relative to the disk. The blades are locked into place axially with bolts, locking pins, etc.
Referring to the prior art arrangement of FIG. 1, a base 1 of a blade is received within a recess established within a disk 2. The base 1 has a plurality of lobes 3a-3f. In the unloaded position shown, the base 1 is biased toward a rotational axis in a direction D, and inwardly facing surfaces of the lobes 3a-3f press against the disk 2. When the base 1 is in a loaded position, the base 1 is biased away from the rotational axis and outwardly facing surfaces of the lobes 3a-3f press against the disk at a respective contact area 4a-4-f. 
In the unloaded position, there are gaps 5a-5f between the lobes 3a-3f and the disk 2 at the contact area 4a-4-f. In the prior art, the size of the gaps 5a-5f does not vary from side to side. In the prior art, some of the lobes 3a-3f experience high loads that can fracture or otherwise damage the base 1 or the disk 2 when the blade is in the loaded position.